They aren't very common.  At least here in the New Braunfels area, floor graphics are not seen very often at all.  I believe one reason for this is because, if overused, they can become eye-sores.  So for this reason, I would limit the amount of this type of advertising unless you honestly have a need to advertise in a way you know will get the public's attention.  They can be installed inside or outside in the weather. Floor graphics, just like wall graphics, are created the exact same way.  The only difference is, the type of media used to print on.  Floor graphic media is a little more rugged than  our normal everyday vinyl, but we print on it exactly the same way.   The other difference is the type of over laminate we apply once the graphic has been printed.  The over laminate is a protective barrier that protects the print, and seals it so nothing will contaminate the print.  Typically, floor graphics over laminate has a couple properties that make it special.   First off, it is thicker for durability and longevity, and it also typically has an anti-slip feature built right into the laminate...almost like sandpaper...watch your step! So next time you see a graphic on the floor, just know it is a little more special and the materials used were very specific for that graphic for you to see!